2-(1-Aryliminoethylidene)quinolylnickel(II) dibromides: Synthesis, characterization and ethylene dimerization capability

A series of 2-(1-aryliminoethylidene)quinoline derivatives (L1–L9) and the nickel(II) dibromides (C1–C9) thereof, were synthesized and characterized. The molecular structures of C2 (R1 = Et, R2 = H, R = Me) and C9 (R1 = iPr, R2 = H, R = iPr) were confirmed as being distorted tetrahedral at nickel by single crystal X-ray diffraction. On treatment with diethylaluminium chloride (Et2AlCl) or ethylaluminum sesquichloride (EASC), these nickel pre-catalysts exhibited high activity for selective ethylene dimerization (0.89–3.29 × 106 g mol−1(Ni) h−1) at 20 °C under 10 atm of ethylene. The influence of the reaction parameters on the catalytic behaviour was investigated for these nickel systems, including variation of Al/Ni molar ratio and reaction temperature.